1. Field of the Invention
The present invention relates to a solid state imaging device having a configuration for transferring a signal charge read out from photodetector parts arranged in matrix, through vertical charge transfer parts. The present invention relates also to a method of manufacturing the solid state imaging device.
2. Description of Related Art
Solid state imaging devices represented by a CCD (charge coupled device) type solid state imaging device have been used widely as imaging elements for imaging apparatuses such as digital still cameras and digital video cameras, and the demands have been increased even more. In addition, due to the demands for coping with moving video pictures of high-definition TV in an imaging device accompanying a trend for the high-definition TV, enhancement in the speed of the transfer frequency has been required for such a solid state imaging device.
As a technique for enhancing the speed of the transfer frequency, namely, a technique for allowing a high-speed transfer, a technique of connecting a shunt wiring and an electrode via a light-shielding film extending in the vertical direction is known (for example, see JP H04-279059 A).
However, in a case of a vertical shunt wiring as shown in JP H04-279059 A, voltages of the same level will not be applied simultaneously to all of the plural light-shielding films connected to the shunt wiring, but the levels of the voltages to be applied vary between the adjacent light-shielding films. Moreover, since the light-shielding films are provided for the respective pixel arrays aligned in the vertical direction, the levels of voltages applied to the portion from the light-shielding films to the interface of the semiconductor substrate at the surface layer side vary between adjacent pixel arrays. As a result, in the solid state imaging device disclosed in JP H04-279059 A, the quantities of electric charge captured by the interface state of the semiconductor substrate and lost at the time of reading out from the photodetector part to the vertical charge transfer part vary from each other between adjacent pixels. This will cause output nonuniformity for the solid state imaging device.
For solving the above-mentioned problems, JP 2006-41369 A discloses a technique of forming a shunt wiring in the horizontal direction.
A solid state imaging device disclosed in JP 2006-41369 A will be described with reference to FIG. 13. In this solid state imaging device, a plurality of photodetector parts 101 are arranged in the horizontal and vertical directions, and transfer channels 102 extending in the vertical direction are arranged between the photodetector parts 101. First transfer electrodes 103a are arranged on the transfer channels 102 and coupled to each other in the horizontal direction in the spacing between the photodetector parts 101. Furthermore, on the transfer channels 102, second transfer electrodes 103b are arranged in the same layer as the first transfer electrodes 103a. 
On each of the first transfer electrodes 103a, shunt wirings 104a and 104b extending in the horizontal direction and corresponding in number to the transfer electrodes are provided. The shunt wirings 104a, 104b have resistances lower than those that of the first transfer electrodes 103a and the second transfer electrodes 103b. The shunt wirings 104a and 104b are connected respectively via connection parts 105 to the first transfer electrodes 103a and the second transfer electrodes 103b on the each of the transfer channels 102.
In a case of configuring a pixel of about 2 μm×2 μm, the width W1 of the first transfer electrode 103a is about 0.45 μm at the portion in the spacing between adjacent photodetector parts 101. The number of the shunt wirings 104a and 104b corresponds to the number of the transfer electrodes arranged for one photodetector part 101, and the number is two in this example. The width W2 of the two low-resistance shunt wirings 104a and 104b is 0.12 μm for example, and the width W3 of the space between the two shunt wirings 104a and 104b is 0.16 μm for example.
In the above solid state imaging device, since the shunt electrodes are not connected electrically to the light-shielding film, the level of voltage applied to the region from the light-shielding film to the interface at the surface of the semiconductor substrate are equal among the respective pixel arrays, and output nonuniformity will not occur.
However, when the technique disclosed in JP 2006-41369 A is applied, the wiring resistance will be increased due to the narrow width effect, because the width W2 of the shunt wirings 104a and 104b is as narrow as about 0.12 μm. This will result in a problem that the speed of transfer frequency cannot be enhanced sufficiently even by using low-resistance shunt wirings.
On the other hand, when the width of the shunt wirings 104 and 104b is increased to a degree not causing a narrow width effect (for example, 0.3 em), the width W1 of the first transfer electrode 103a also should be increased (for example, 0.8 μm). This will result in another problem that the opening width is decreased and the smear property and the sensitivity deteriorate.